Safety device for screw jacks



Nov. 26, 1929. F. GORMLEY 1,737,153

SAFETY DEVICE FOR SCREW JACKS Filed Jan. 6. 1928 Fly. 1.

liwenlor: Irmlkl. Gormley,

Patented Nov. ltiil FATET OFFECE FRANK L. G GR-MLEY, OF CHICAGO,ILLINOIS, ASSIGNOR TO THE BUDA COMPANY, OF HARVEY, ILLTNOES, ACORPORATION OF ILLINOIS SAFETY DEVICE FOR SCREW JACKS Application filedJanuary 6, 1928. Serial No. 244,860.

This invention relates to journal or other jacks which heretofore havenot been provided with means for retarding the lowering of the liftingscrew under the weight of the load, the object of the present inventionbelng the provision of simple but effective means for preventing theaccidental turning of said lifting screw and particularly when the screwhas become worn.

This object is attained by the mechanism illustrated in the accompanyingdrawing.

For the purpose of illustrating the invention, one preferred formthereof is illustrated in the drawings, this form having been found togive satisfactory and reliable results, al-

. though it is to be understood that the various instrumentalities ofwhich the invention consists can be variously arranged and organized,and the invention is not limited to the precise arrangement andvorganization of these instrumentalities as herein shown and describedexcept as required by the scope of the appended claims.

Of the drawings: t

Figure 1 represents a vertical section of a lifting jack embodying theprinciples of the present invention, and

Figure 2 represents a partial horizontal.

section on line 2, 2, on Fig. 1.

Similar characters indicate like parts throughout the several figures ofthe drawings.

- In the drawings 10 is a casing having a cylindrical bearing at itsupper end in which the standard 11 is adapted to reciprocate, saidstandard being prevented from turning about its axis by the key 12secured to casing 10 and projecting into the vertical slot 13 ofstandard 11.

The lower end ofthe standard 11 has secured therein a nut 1 f coactingwith the rotatable steep pitch screw 15, the lower end of which haskeyed thereto a bevel gear 16 meshing with another bevel'gear 17 formedupon the inner end of a driving shaft 18 revoluble in a bearing in thecasing 10 and having an actuating device 19 on the outer endthereof.

The actuating device which preferably is used on this driving shaft 18is that shown in another application of mine, filed Dec. 21, 1926 andnumbered 156,109 towhich reference may be made as to construction andoperation.

The gear 16 rests upon a bearing plate or disk 20 superimposed upon aplurality of balls 21 disposed in a circular track formed in the upperface of another plate or disk 22 supported upon the removable bottom 23of the casing 10.

This bottom member 23 is preferably threaded to the lower part of thecasing as indicated at 24.

The threads of the lifting screw 15 in a jack of this character mustnecessarily have a coarse pitch in order to maintain speed when liftingand lowering and still have the jack compact as otherwise it would benecessary to use gears of much greater diameter if the pitch of thescrew threads is reduced.

This would necessitate making the lower end of the casing of greaterdiameter, therer by increasing the weight of the jack and making itawkward to handle.

Moreover, it would be so bulky that it could not be used in some places,especially in close quarters where there would not be room for theactuating device 19 to be operated to run its standard up to and fromthe load to be raised.

With this steep coarse pitch of thread in screw and its coacting nut 14a certain amount of wear takes place between these two members after thejack has been in use some time due to the frictional contact between thecontacting screw threads and nut threads.

This is very objectionable for the reason that as the wear increasesthere is a tendency for the standard 11 having a load thereon to causethe screw 15 to turn and thereby accidentally lower the load.

Some means therefore should be provided in jacks of this character toprevent this accidental lowering and one way of accomplishing this isshown in the drawings.

To this end bosses 25 are formed upon the casing 10 these bosses 25having recesses 26 therein in which are disposed the shanks 27 of shoes28, the inner faces of which are curved to fit the periphery of thebearing plate 20 on which the gear 16 rest-s and with which it is infrictional contact.

The bosse 25 are in alinement and on opposite sides of the casing 10.

Surrounding each shank 27 is a coiled spring 29 which forces the shoe 28into contact with the periphery of the bearing plate 20.

The outer ends of the bosses 25 have threaded plugs 30 which may beadjusted to vary the tension of the springs 29.

There is sufficient frictional contact between shoes 28 and the plate 20to prevent this plate from turning under normal conditions but when aload is on the standard the friction between the gear 16 and plate 20exceeds the friction between the shoes 28 and plate 20 so that saidplate 20 will rotate with said gear during the raising and lowering ofthe load by rotating the ear 17 and the driving shaft 18.

WVhen the main screw 15 is not rotated by manual power the frictionbetween shoes 28 and plate 20 will be sufhcient to prevent any rotationthereof under the weight of the load and this is true even when thethreads of screw 15 and nut 1 1- are practically worn out.

This friction between the shoes 28 and plate 20 is also sufficient toovercome the frictional contact between ratchet and pawl in theactuating device 19 so that the standard 11 may be raised by shortstrokes of said actuating device.

Parallel flanges 31 extending inwardly from the casing 10 and contactingwith the upper and lower faces of the shoes 28 prevent these shoes fromturning about the axes of the shanks 27.

The friction devices are shown coacting with the periphery of thebearing plate 20 and this is the preferred construction but it is quiteobvious that said friction devices may be applied to some othercylindrical member rotating with the main screw 15 and accomplish thesame results.

It is believed that the operation and many advantages of the inventionwill be understood without further description.

Having thus described my invention, I claim:

1. In a lifting jack including a casing, a

vertically movable standard, and a rotatable member within the casingfor moving said standard; a cylindrical plate rotatable with saidmember; shoes on opposite sides of said plate; and means supported bysaid casing for forcing said shoes into frictional contact with theperiphery of said plate and preventing its rotation under normalconditions.

2. In a lifting jack including a standard and a rotatable steep pitchscrew for raising said standard enclosed within'a casing; a gear 7rotatable with said screw; a cylindrical member in frictional engagementwith said gear i and adapted to rotate therewith; and yielding meanssupported by said casing and in frictional contact with the periphery ofsaid member.

3. In a lifting jack including a standard and a rotatable steep pitchscrew for raising said standard enclosed within a casing; a gearrotatable with said screw; a cylindrical member in frictional engagementwith said gear and adapted to rotate therewith; yielding means supportedby said casing on opposite sides of said member and in frictionalcontact therewith; and means for varying said frictional contact.

4. In a lifting jack including a standard and a rotatable steep pitchscrew for raising said standard enclosed within a casing, said casinghaving oppositely disposed cylindrical recesses with parallel inwardlyextending flanges; a gear rotatable with said screw; a cylindricalmember in frictional engagement with said gear and adapted to rotatetherewith; and yielding means supported in said recesses and includingshoes disposed between I said flanges and having curved faces in fricadriving gear ke ed thereto; a bearing plateupon which saic gear rests;and yielding means within and supported by said casing consisting inpart of a shoe in frictional contact with the periphery of said bearingplate.

6. In a lifting jack including a standard, a rotatable steep pitch screwfor raising said standard enclosed within a casing and having a drivinggear keyed thereto; a bearing plate upon which said gear rests; shoes onopposite sides of said plate; and yielding means in recesses formed insaid casing adapted to force said shoes into frictional contact with theperiphery of said plate.

7 In a lifting jack, a casing containing an elevating and loweringmechanism consisting in part of a rotatable cylindrical member; andyieldingmeans supported disposed between inwardly extending flanges onsaid casing and having elongated curved surfaces in frictional contactwith the member.

8. In a. lifting jack, a casing containing means for elevating andlowering a load supporting standard, consisting in part of a rotatablegear; a cylindrical plate in'frictional engagement with said gear andnormally rotatable therewith; a device within said casing in frictionalengagement with said plate, the degree of friction being less betweensaid device andplate than between said plate and gear; and means for;manually rotating said gear and overcoming the friction between saidvice from said plate.

9. Inalifting jack, a casing containing periphery of said means forelevating and lowering a load supporting standard, consisting in part ofa rotatable gear; a plate in frictional engagement With the lower sideof said gear, said frictional engagement being increased When saidstandard is supporting a load; a device supported by said casingcoacting with the periphery of said plate and creating a frictionthereon sufficient to prevent normal rotation of said gear; and manuallyactuated means for rotating said gear and overcoming the frictioncreated by said device Without disenga ing said device from said plate.

igned by me at Harvey, Illinois, this 3rd day of January, 1928.

FRANK L. GORMLEY.

